Oil burner control circuit with small ignition transformer



Sept. 25, 1951 E 2,568,954

OIL BURNER CONTROL CIRCUIT WITH SMALL IGNITION TRANSFORMER Filed Aug. 2, 1947 2 Sheets-Sheet 1 INVENTOR. HOWARD E. EARL F) 7" TORNE V Sept. 25, 1951 H. E. EARL 2,568,954

OIL BURNER CONTROL CIRCUIT WITH SMALL IGNITION TRANSFORMER Filed Aug. 2, 1947 I 2 Sheets-Sheet 2 I INVENTOR. HOWARD E. EARL 14 7' TOPNEV Patented Sept. 25, 1951 OIL BURNER CONTROL CIRCUIT WITH SMALL IGNITION TRANSFORMER Howard E. Earl, Bloomington, Ill., assignor to Eureka Williams Corporation, Bloomington, Ill., a corporation of Michigan Application August 2, 1947, Serial No. 765,711

7 Claims. 1

This invention relates to oil burner controls and is particularly related to control circuits of the intermittent ignition type having electrically controlled elements by the employment of which ignition transformers of less than the usual size and cost may be employed.

Heretofore it has been customary in the ignition control circuits of the intermittent ignition type to employ transformers constructed in such manner as to be capable of operation continuous- 1y, even though such transformers are subject to service under normal conditions only for a very short period of time.

It is the purpose of the present invention to discontinue the employment of transformers of such excessive size and cost in intermittent ignition type oil burner apparatus.

The invention contemplates the employment in intermittent ignition type oil burners of small size transformers, these being only a fraction of the size of transformers now customarily employed in such intermittent ignition type oil burners. To make possible the use of such transformers in intermittent control type oil burner apparatus there is employed a temperature responsive means or device located in such position with respect to the transformer employed that the control circuit will be broken whenever the transformer is subject to operation for any period longer than that for which the transformer is rated. As a result of the operation of such temperature responsive means it will be impossible for a transformer to increase in temperature to a greater extent than the predetermined safe operating temperature for such transformer. Also by the employment of such temperature responsive means it will be impossible to use controls designed for operation with continuous ignition oil burners because in such event the temperature responsive means employed with a transformer will simply render the control circuit inoperative for continuous operation.

An object of the invention, therefore, is to provide an oil burner control circuit of the intermittent ignition type with which a smaller and less expensive transformer may be safely and efficiently employed, than it is now possible to employ in connection with oil burners of the intermittent ignition type.

Another object of the invention is to provide anintermitt-ent ignition type oil burner in which the over-all cost of the various burner and control elements may be materially reduced.

Other and further objects of the invention will be apparent by reference to the accompanying drawings of which there are two sheets, which by way of illustration show preferred embodiments and th principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims. I also contemplate that of the several different features of my invention, certain ones thereof may be advantageously employed in some applications separate and apart from the remainder of the features.

In the drawings:

Fig. 1 is a diagrammatical illustration of the elements of an oil burner apparatus having an oil burner control circuit embracing the principles of the invention;

Fig. 2 is a similar view of an oil burner apparatus illustrating another form of oil burner control circuit which the invention may assume;

Fig. 3 is another similar view of an oil burner apparatus illustrating another form of oil burner control circuit which the invention may assume; and i Fig. 4 is a cross sectional view illustrating another form of temperature responsive means which may be employed in the apparatus and circuits illustrated by Figs. 1 to 3.

Referring to Figs. 1, 2 and 3, there is diagrammatically illustrated oil burning apparatus, including motors II, ignition transformers I2, primary controls I3, room thermostats I4, line voltage limit controls IB, and burner ignition apparatus II. V

In all of these structures the primary control I3 includes a transformer I8, a stack switch III, a relay switch 2|, an ignition timer 22, a resistor 23, a thermal safety switch 24, and pairs of terminals I--2, 3-4, and 5-5. MI is a latch member spring biased toward the contact bars 34 and permitted to abut the end of the latter when the relay 2| is energized. During the ignition period the contact bars 34 warps upwardly breaking the ignition circuit by opening switch 22. Member 3 then moves under the contact bars 34 and holds switch 22 open until deenergization of relay 2| upon completion of a running cycle.

The primary control I3 herein illustrated is conventional and illustrates one type of this contro which is now commonly in use.

The transformers I8 embrace primary and secondary windings and 26. The stack switch it includes electrical contact elements 28 adapted to open and close electrical circuits in response to the operation of thermally responsive elements 29 adapted to be located within or in thermal contact with the stack of a furnace with which the oil burner is employed. Relay switches 2| embrace relay coils 3| and armatures or cores 32 having contact elements 33 adapted to open or close electrical circuits in response to the movement of the armature 32. Ignition timers 22 embrace thermally responsive contact bars 34 adapted to make or break electrical circuits in response to the flow of electrical energy through the coils of timer switch heaters 38 associated therewith. Thermal safety switches 24 embrace thermally actuated conductors 31 adapted to be moved in response to the temperature of heaters 38 and 40 associated therewith and in response to the movement thereof to a predetermined extent, to open the circuit therebetween by dislocating from normal position manually operable reset levers or means 38.

The primary controls |3 have the elements thereof previously described wired in circuits in accordance with the arrangement of the various conductors illustrated by Fig. 1. The primary controls l3 included in the apparatus illustrated in Figs. 2 and.3 are also connected in circuits similar to the circuits illustrated by Fig. 1.

Room thermostats l4, line voltage limit switches l8, motors II, and igniters employed in the apparatus illustrated in Figs. 1, 2 and 3 are all conventional elements such as those now generally employed in conventional oil burner apparatus.

The ignition transformers l2 all include primary windings 4|, secondary windings 42, transformer casings 43, igniter terminals 44 and 48, terminal members 41 and temperature responsive means or thermostatically actuated switches 48.

As illustrated by Figs. 1, 2 and 3, the thermostatically actuated switches 48 comprise switch boxes 49 secured in openings formed in the transformer casings 43 in such position that the switch boxes 49 are closed by covers 5| secured to the casings 43 by screws 52. The thermostatically operated switches or temperature responsive means 48 are located within the switch boxes 48 and comprise arcuate bimetallic contact bars 53 having terminals 54 at opposite ends thereof adapted when in closed position to close electrical circuits between pairs of terminals 58 secured in insulated relation to one another within the boxes 43. The bimetallic bars 53 are mounted at their mid portions upon studs 51 secured in the boxes 48 in such position as to allow the contact bars to move to make and break an electrical circuit through the terminals 54 and 58. The switches 48 may include heaters 58 coiled around the insides of the switch boxes 43 in such position as to heat the bimetallic bars 53 in response to an increased flow of electrical energy through the heaters for the purpose of reducing the response time of the bimetallic bars 53 in the event this is desirable. The heaters 53 to effect such operation of the bimetallic bars 53 may be connected in series with the terminals 58 as is indicated in Figs. 1, 2 and 3.

It will be apparent that the switch boxes 48 are so positioned in the transformers 2 that the thermostatic elements or switch bars 53 will be affected by the temperature of the transformers,

this being true particularly in view of the fact that the boxes 49 are in direct thermal contact with the transformer casings 43, as the result of which variations in temperature of the various elements of the transformers |2 will be directly conducted to the thermostatic elements 53 by direct and positive contact of the various associated parts. Thermostatic bars 53 and heating coils 58 are so positioned in the boxes 48 and are so calibrated with respect to one another and to the transformers |2 that any increase in temperature in the transformers that is greater than an allowable temperature at which a transformer will operate in an oil burner apparatus will cause immediate snap action movement of the bars 53 into such position as to open the circuits between the terminals 58.

In the structure disclosed by Figs. 1, 2 and 3, the switch bars 53 of the thermostatic elements 48 are of the automatically reclosing ty that is, they are constructed in such manner that when the temperature thereof decreases to a predetermined value, then the bars will again snap into switch closing position and in which position the circuit is again closed between the contacts 58. Such predetermined temperature will occur in the bars 53 when the transformers l2 have cooled to such an extent that it may be considered safe enough to again operate the transformers for the normal period required for oil burner ignition and during which time it may be possible that the oil burner will ignite without causing excessive temperatures in the transformer such as would result in breaking the electrical circuit between the contacts 58 and the thermostatic bar 53 thereof.

While only one type of thermostatic element has been illustrated in the drawings, this type being the bimetallic bars such as are indicated at 53, it will be apparent that any type of thermostatic elements may be employed, such as thermostatic discs, expansible column elements and other thermostatic devices now generally available for such purposes.

In the structure disclosed by Fig. 4, the thermostatic element 53 is constructed in such manner as to normally close the circuit between the contacts 56 when a transformer is being operated under normal conditions. In the event the temperature of the transformer increases beyond a desirable or predetermined temperature, then the thermostatic element 53 will snap open as previously described and in such manner as to open the circuit between the terminals 58. However, the element 53 in this structure is so constructed that it will not return to its normal current closing position at normal temperatures usually aifecting a burner transformer. In this structure it is necessary to manually reset the switch, this being madepossible by the operation of a manually operable button 8| projecting from a disc 82 located inside the switch box 43. The button 8| projects through an opening in a switch box cover II. It will be apparent from the drawing that when the button 8| is depressed the disc 82 will engage the thermostatic element 53 and will force the same over its normal dead center position. Under such circumstances the element 53 will snap into contact closing position and electrical current again will be able to flow between the contacts 58 through the element 53.

The structure disclosed by Fig. 4 may be employed instead of the temperature responsive means 48 disclosed by F s. 1, 2 and 3, and in such event the circuits between the contacts 58 auoapu will be automatically broken when the temperature of the transformers reaches a predetermined value, but such circuits will not be automatically closed as in the structures now disclosed by Figs. 1, 2 and 3. Instead of this it will be necessary to close the circuits manually by manipulating the switch buttons 8|.

In the structure disclosed by Fig. l the motor II, the transformer l2, the primary control l3, the thermostat l4 and the limit switch l6 are all connected by electrical conductors as indicated in the drawing and in such manner that the temperature responsive means 48 is connected in series with the common line leading to both the ignition transformer and the burner motor.

In the structure disclosed by Fig. 2 the temperature responsive means 48 is connected in series with the individual line to the motor.

In the structure disclosed by Fig. 3 the temperature responsive means 48 is in series with the limit switch in the hot line to the primary control.

The primary control I3 employed in connection with the apparatus disclosed by Figs. 1, 2 and 3 is of a well known type in which stack temperature is employed in such manner as to actuate the control for the purpose of producing intermittent ignition in the oil burner circuit. However, the invention may be employed with any other type of primary control or may be employed with such devices as resistors or photocells, these being now available and sometimes employed in connection with oil burner circuits of the intermittent ignition type.

The primary control disclosed operates as follows: Upon closing the room thermostat, the current is allowed to flow through the primary coil of the transformer I8, thus energizing the relay coil 3|, which closes the contact bar of the relay thereby allowing the current to flow to both the motor II and the ignition transformer l2. Also upon closing the circuit through the relay coil 3|,

the heater coils 36 and 40 through the relay coil 3|, the heater coils 36 and 40 of the ignition timer 22 and the thermal safety switch 24 respectively are energized. When the heater coil 36 reaches a predetermined temperature the circuit is broken through the bimetallic switch element 34, and this opens the circuit to the ignition transformer.

As the burner flame is established the thermally responsive element 28 of the stack switch Ill actuates to close the switch element 28, and this allows current to flow through the heater 38 of the thermal safety switch 24, and this compensates for the flow of current through the heater 40 and prevents the opening of the switch element 39. When room temperature is increased to reach the temperature at which the room thermostat is set to open the circuit therethrough, the thermostat operates to deenergize the relay 3 I, and this opens the circuit to the motor I I. In the event of flame failure or faulty ignition, the circuit is not established through the contact element 28 of the stack switch l9, and the element 38 of the safety switch 24 will be actuated in response to the operation, of the heater 4!] in such manner as to open the safety switch 24, thereby shutting off the current to the primary control. The contact element 39 requires manual resetting in order to reset the primary control in such manner as to be operable upon the closing of the circuit through the room thermostat.

In the structure disclosed by Fig. 1 the thermally responsive means or switch 48 will open to break the circuit between the contacts 56 in the event 6 the primary control ignition circuit fails to function properly. Otherwise the transformer would continue in operation, thereby increasing in temperature to a greater than desired extent as a result of such failure of the primary control ignition circuit.

However, under such circumstances the transformer l2 will not burn out or become shorted or otherwise operate in such manner as to be dangerous either to the transformer or to the entire apparatus and the house in which the apparatus is employed. Before such might occur however, the thermally responsive means 48 will be affected in such manner as to open the circuit between the contacts 56, and in the structure disclosed by Fig. 1 this action will result in breaking the circuit in the common line to the ignition transformer and the burner motor. When this occurs the burner will shut down and under such circumstances the element 29 of the stack switch l8 will cool to such an extent as to open the circuit through the contact member 28. With this circuit open the heater coil 40 of the safety switch 24 will be deenergized, and this will break the power circuit to the primary control. When the circuit is broken in this manner the primary control will be out of operation until the circuit through the safety switch 24 is reestablished by manually closing the resetting switch element 39.

In the structure disclosed by Fig. 2 the operation of the circuit through the thermally responsive means 48 immediately opens the circuit to.

the burner motor ll, causing the burner to shut down and this in turn allows the element 23 of the stack switch I9 to cool to such an extent that the switch element 28 will be opened. The opening of the switch element 28 results in opening the circuit through the primary control until the switch element 39 is reset as previously described.

In the structure disclosed by Fig. 3 the opening of the circuit through the thermally responsive switch or means 48 immediately cuts off the power to the primary control 13, thus causing a complete shut down of the burner. The circuit may be automatically reestablished when the transformer l2 cools suiiiciently to cause the switch bar 53 to close automatically as is disclosed in Figs. 1, 2 and 3 or when the reset button or member 6| is depressed as is disclosed by Fig. 4.

While I have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. The combination of an oil burner control circuit of the intermittent ignition type comprising an ignition primary circuit including an ignition transformer, with a supply circuit including a voltage source for the ignition transformer such that said ignition transformer will overheat if continuously operated, and means responsive to the temperature of said transformer for opening said ignition circuit so as to deenergize said transformer when the temperature of said transformer increases beyond a predetermined safe operating value.

2. The combination of an oil burner control circuit of the intermittent ignition type comprising an ignition primary circuit including an ignition transformer, with a supply circuit including a voltage source for the ignition transformer such that nsformer will overheat if continual. and means responsive to the ten-i are e of said transformer for opening said ignition circuit so as to deenergize said transformer when the temperature of said transformer increases beyond a predetermined safe operating value and for closing said-circuit when the temperature of said transformer decreases below a predetermined value.

3. The combination as set forth in claim 1 with a manually operable means for closing said ignition circuit after such circuit has been opened by said temperature responsive means.

i. The combination of an oil burner control circuit of the intermittent ignition type comprising an ignition primary circuit including an ignition transformer, with a supply circuit including a voltage source for said ignition transformer such that said ignition transformer will overheat if continuously operated, said transformer having primary windings energized by said primary circuit, and means actuated by the flow of electrical energy through said primary windings for opening said primary circuit through said primary windings to deenergize said transformer in response to a predetermined temperature of said transformer.

5. The combination of an oil burner control circuit of the intermittent ignition type comprising an ignition primary circuit including an ignition transformer, with a supply circuit including a voltage source for the ignition transformer such that said ignition transformer will overheat if continuously operated, a burner motor in said control circuit, and temperature responsive means connected in series with said burner 8 motor and said ignition transformer for rendering said burner motor and ignition transformer inoperative in response to a predetermined temperature of said ignition transformer.

6. An oil burner control circuit as defined in claim 5, in which said temperature responsive means is provided with a manually operable reset member for moving said temperature responsive means into circuit closing position upon the cooling of said transformer to a predetermined temperature.

7. The combination of an oil burner control circuit of the intermittent ignition type comprising an ignition primary circuit including an ignition transformer, with a supply circuit including a voltage source for the ignition transformer such that said ignition transformer will overheat if continuously operated, a burner motor in said control circuit, and temperature responsive means'in series with said motor for rendering said burner motor and ignition transformer inoperative in response to a predetermined temperature of said ignition transformer.

HOWARD E. EARL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,793,011 Ray Feb. 17, 1931 2,198,556 Cunningham Apr. 23, 1940 2,268,229 Walle Dec. 30, 1941 2,298,229 Putnam et a1. Oct. 6, 1942 2,333,537 Leonard Nov. 2, 1943 2,369,530 Bulger Feb. 13, 1945 

